At the present liquid crystal compounds are applied to various apparatuses as a displaying material and put to practical use in watch, personal calculator, small size television receiver and the like. These apparatuses use a cell containing a liquid crystalline material composed mainly of nematic liquid crystal and adopt a display system called as TN type or STN type. In this case, the operation of the cell is based on a weak interaction (.DELTA..epsilon.E.sup.2 /2) between dielectric isotropy .DELTA..epsilon. and electric field E, so that the cell has a drawback that the response time to the electric field is as slow as few msec. Therefore, when the cell is applied to the television receiver, an active matrix system in which many switching elements are arranged at respective pixels is generally used as the cell driving system, which becomes an obstruct for realizing a large size display screen. However, a liquid crystal cell having a high response time of p sec order and a property not changing orientation of liquid crystal molecule even in the switching-off of the electric field (memory property) is made possible by appearance of ferroelectric liquid crystals representing 4-(4-n-decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) synthesized by R. B. Meyer et al in 1975 and a new displaying system using these liquid crystals as proposed by N. A. Clark (Applied Phys. Lett. 1980, 36, 899). When employing the displaying element with these materials, it is possible to realize a liquid crystal television receiver with a simple matrix system in which a multiplex driving mode is used without using the switching elements, which is fairly advantageous as compared with the active matrix system in view of productivity, cost, reliability, formation of large size display screen and the like.
Therefore, many ferroelectric liquid crystalline materials are synthesized and proposed up to the present. In order that these ferroelectric liquid crystalline materials are used as a displaying material, they are required to have some properties, among which a large spontaneous polarization over a wide temperature range and a chemical stability are fundamentally required. In a greater part of the early ferroelectric liquid crystals, however, the spontaneous polarization was as small as not more than 10 nC/cm.sup.2, and they were chemically unstable because Schiff's base was existent in their molecules. Further, in order to provide the ferroelectric liquid crystal, it was required to introduce an optical active group, and in this case 2-octanol and 2-methyl butanol derivatives were mainly used as an asymmetric source.
Recently, there is reported the appearance of large spontaneous polarization through chemically stable ester compounds. For instance, a compound having the following formula: ##STR4## forms a liquid crystal of chiralsmectic C phase over a temperature range of 78.7.degree..about.103.3.degree. C. and of cholesteric phase over a temperature range of 103.3.degree..about.120.8.degree. C., and the spontaneous polarization at 83.degree. C. of this liquid crystal is 89 nC/cm.sup.2 (Japanese Patent laid open No. 61-43).
Furthermore, a compound having the following formula: ##STR5## forms a liquid crystal of smectic E phase over a temperature range of 75.5.degree..about.91.5.degree. C., of chiralsmectic H phase over a temperature range of 91.5.degree..about.107.0.degree. C. and of chiralsmectic C phase over a temperature range of 107.0.degree..about.129.2.degree. C., and the spontaneous polarization at 119.2.degree. C. of this liquid crystal is 184 nC/cm.sup.2 (Japanese Patent laid open No. 60-149,547).
In these compounds, the temperature range forming the chiralsmectic C phase is about 20.degree. C. and can not be said to be sufficiently wide though the latter compound has particularly a large spontaneous polarization.
On the other hand, as to phenylpyrimidine series compounds, there is reported an example exhibiting the chiralsmectic C phase at about room temperature.
For example, a compound having the following formula: ##STR6## forms a liquid crystal of chiralsmectic C phase over a temperature range of 40.7.degree..about.82.8.degree. C. and of smectic A phase over a temperature range of 82.8.degree..about.89.1.degree. C., but it is presumed that the response time at 43.degree. C. of this liquid crystal is as slow as 1,500 ps and the spontaneous polarization is fairly small (Japanese Patent laid open No. 61-200,973).
In addition, there is proposed a compound developing a large spontaneous polarization by using an asymmetric carbon source different from the conventional one, i.e. amino acid and having the following formula: ##STR7## (Japanese Patent laid open No.61-165,350). This compound forms a liquid crystal of highly smectic phase over a temperature range of 33.degree..about.36.degree. C., of chiralsmectic C phase over 36.degree..about.52.degree. C. and of smectic A phase over 52.degree..about.66.degree. C. and develops a large spontaneous polarization of 220 nC/cm.sup.2, which is highest among ones reported up to date, at a temperature lower by 19.degree. C. from a phase transition point to the chiralsmectic C phase on cooling. This compound exhibits the chiralsmectic C phase at about room temperature, but the temperature range can not be said to be wide. Furthermore, it is chemically unstable because carbon-chlorine bond is contained in the alkyl chain. In general, when the spontaneous polarization is about 200 nC/cm.sup.2, there is frequently a case of existing highly smectic phase beneath the chiralsmectic C phase, which may have a bad influence on the production of the liquid crystal composition.
Moreover, some liquid crystal compounds having a ketone group directly bonded to benzene ring in their molecules are proposed. For instance, the following compounds are reported as a compound having a ketone group and exhibiting Sc phase (Dietrich Demus et al., "Flussige Kristalle in Tabellen I and II", Grundstoffindustrie, published on 1974 and 1984). ##STR8##
It is described that the compound of the above formula (a) shows a liquid crystal state only in the cooling when n is 9 or 10, and the compound of the formula (b) shows a liquid crystal state when n is 8, 9 or 15, and the compound of the formula (c) shows a liquid crystal state only in the cooling when n is 3.about.9. However, these compounds have not an asymmetric carbon and do not develop ferroelectricity. And also, there is proposed a compound having a ketone group and an asymmetric carbon in its molecule and represented by the following formula: ##STR9## (Japanese Patent laid open No. 60-13,729).
This compound has the asymmetric carbon at its .beta. position and exhibits a chiralsmectic C phase at 68.3.degree. C. only in the cooling, but the value of spontaneous polarization is not known.
A compound having the following formula is also reported (Japanese Patent laid open No. 61-251,672). ##STR10##
This compound forms a liquid crystal of chiralsmectic C phase over a temperature range of 67.degree..about.69.degree. C. and of smectic A phase over 69.degree..about.79.3.degree. C. and the response time at 61.degree. C. of this liquid crystal is as slow as 200 .mu.sec, from which the spontaneous polarization is presumed to be fairly small.
The above various compounds have problems that the response rate as a liquid crystal is slow because of a relatively small spontaneous polarization, the stability to light is generally lacking owing to the presence of carbon-halogen bond, the temperature range showing the ferroelectricity is narrow, highly chiralsmectic phase is existent at low temperature side of chiralsmectic C phase, and the like.
The inventors have made various studies in order to solve these problems and found that compounds having an asymmetric carbon in u position and a ketone group directly bonded to benzene ring in molecule are surprisingly stable to light or the like, enantiotropic and wide in the temperature range showing a liquid crystal state, and particularly forms a ferroelectric liquid crystal having a large spontaneous polarization and a fast response rate when the alkyl group is an optical active group, and that a compound showing no highly chiralsmectic phase at low temperature side of chiralsmectic C phase or directly transiting from chiralsmectic C phase to crystal is existent among these compounds.
The invention is based on the above knowledges and is to provide novel alkanoyl ester compounds, a liquid crystal composition containing this compound, intermediates for these compounds and a method of producing the same.